Kate Middleton's family has had a coat of arms designed, which will feature on a souvenir royal wedding programme.

Her father Michael commissioned the heraldic design to mark his daughter's marriage to Prince William on 29 April.

It features three acorn sprigs, one for each of the Middletons' children: an idea Miss Middleton suggested.

Royal experts say the coat of arms - which cost £4,400 to make - marks the increased social status of her parents and her potential as a future queen.

Thomas Woodcock, Garter Principal King of Arms, from the College of Arms in the City of London, helped the Middletons with the design.

He said the oak tree was a traditional symbol of England and a feature of west Berkshire, where the family have lived for 30 years.

Mr Woodcock said the gold chevron in the centre of the coat of arms signified Miss Middleton's mother, Carole, whose maiden name was Goldsmith.

Kate's coat of arms includes a tied ribbon, showing she is an unmarried woman, and features three acorn sprigs, representing each of the Middleton children. At its centre is a gold inverted "V" reflecting Kate's mother Carole's maiden name of Goldsmith and white chevronels, symbolising mountains, representing the family's love of the Lake District and skiing

William's coat of arms has a design derived from that of his father, the Prince of Wales, and has a main shield featuring the three lions, lion rampant and harp stringed argent of England, Scotland and Ireland. It also has the lion and unicorn supporters - symbols of the UK. The white label features a sea shell or "escallop", taken from the family coat of arms of his mother, Princess Diana. The blue garter symbolises his appointment at Knight of the Garter

White chevronels - narrow chevrons above and below the gold chevron - symbolise peaks and mountains, and the Middleton family's love of the Lake District and skiing.

Mr Woodcock said: "It's not compulsory, but as their daughter is marrying into the Royal Family she will have a need probably to use a coat of arms."

He said Miss Middleton could have been granted her own heraldic design but her father wanted the whole family to be able to use it.

Elaborate lozenge

A version of the coat of arms, which can only be used by Kate or her sister Pippa as it denotes a Middleton spinster, will be printed on the back of the souvenir programme. Prince William's will be on the front.

Miss Middleton's heraldic design features a tied ribbon to show she is an unmarried woman.

Overall, it is designed like an elaborate lozenge rather than a shield, a shape reserved for men.

She will be able to use the coat of arms up until her wedding day, after which it will be combined with that of Prince William.

Mr Woodcock said: "With any new design of a coat of arms you have to make sure that the design is distinct not just in colour but in the linear appearance.

"And, as there is a 16th Century coat of arms with a chevron between three sprigs of oak, we've made the differences - dividing the background colours."

Multimedia nuptials

Broadcast footage of the wedding will be streamed live on the royal YouTube channel, accompanied by a live blog put together by staff at Clarence House and St James's Palace.

The commentary will provide historical information and links to previously unpublished photographs and video footage with live updates on social media sites such as facebook and twitter.

People have put Coats of Arms on their watering cansPeter Hunt, BBC Royal correspondent